I can't add transmission fluid to my 2004 saturn vue

I think your transmission is a 4T45E which does not have a typical dipstick. Check underneath the vehicle on the transmission case above the oil pan on the passenger side of the vehicle and you will see a pipe thread plug. The transmission must be at operating temperature on a level surface and the engine running, you then remove the plug and add new fluid in the fill hole until it runs out the removed plug. You will obviously need a catch basin and do not re-insert plug until fluid has stopped overflowing. Do not turn off the engine during the process.